The drive circuit of this type of electric compressor is accommodated in a metal housing. The drive circuit has an external connector to be electrically connected to a vehicle battery, which is an external power source. Electrical components on the circuit board receive electric power via the external connector. An inverter circuit for driving the electric motor and a switching element for performing switching control of the inverter circuit are mounted on the circuit board. Also, a filter coil and filter capacitors are mounted on the circuit board. The filter coil and the filter capacitors are filter elements, which protect switching elements from instantaneous and excessive currents and reduce noise.
As described above, a great number of electric circuits and electrical components are mounted on the circuit board of a drive circuit. Since the sizes of filter coils and filter capacitors are large, the circuit board has adhesive applied thereon to reduce vibration and parts having auxiliary functions for fixing the board with bolts. As a result, circuit boards tend to be large.
Accordingly, to reduce the size of circuit boards, for example, Japanese Laid-Open Patent Publication No. 2007-309125 discloses an on-vehicle electric circuit unit mounted on an electric compressor. A circuit board and electric elements are accommodated in a housing formed by an upper case and a lower case. A power inputting terminal is fixed to the upper case. The power inputting terminal is an external connector that is electrically connected to an external power source. The power inputting terminal is also connected to a filter coil, filter capacitors, and an inverter control board, which is a circuit board, via a busbar.
The filter coil of an on-vehicle electric circuit unit is fixed to the upper surface of the upper case with fixing members. The filter capacitors are fixed to a side of the upper case with other fixing members. Therefore, compared to, for example, a case where a filter coil and filter capacitors are mounted on one component side of an inverter control board, the size of the component side is reduced. That is, the size of the inverter control board is reduced.
However, according to the electric compressor disclosed in the document, the filter coil and the filter capacitors are fixed to the upper case, or to the housing, while being pressed against the inner wall of the upper case. Therefore, when the coatings of the filter capacitors and the filter coil are worn due to vibrations applied from the outside, the electrical insulation of the housing, which contacts the filter capacitors and the filter coil, is difficult to maintain.